1. Field of the Invention
The present invention relates to a new and useful class of corrosion inhibitors, and a process of using them. More particularly, the present invention concerns novel compositions of matter which reduce the attack of aqueous acid solutions on ferrous metals, and a process of using them.
2. Technology Review
In the exploration and recovery of oil from underground fields, it is common to "acidize" both new and producing wells with aqueous solutions of strong acids. Various inhibitors for preventing the attack of acids on ferrous metals have been proposed. Of the many inhibitors especially designed to prevent acid attack on the well casings, very few provide satisfactory protection. Arsenic and/or various arsenic compounds were used as corrosion inhibitors, despite their toxic effect. The toxic nature of arsenic and its compounds, and their adverse effect on catalysts used in petroleum refineries, have caused an extensive search for new corrosion inhibitors.
U.S. Pat. No. 3,077,454 discloses a class of inhibitors comprising certain active nitrogen-containing compounds combined with organic ketones and an aliphatic or aromatic aldehyde, capable of reducing aqueous acid attack on metals.
U.S. Pat. No. 4,493,775 discloses a formulation including (A) a reaction mixture prepared by reacting a formaldehyde component, an acetophenone component, a cyclohexylamine component and, optionally, an aliphatic carboxylic acid component, and (B) an acetylenic alcohol and excess (unreacted) formaldehyde. A C.sub.1 -C.sub.4 alkanol, a surfactant, or other inert compound, may optionally be present in the formulation. The formulation is a corrosion inhibitor which is especially effective in sour wells, where hydrogen sulfide corrosion is a potential problem.
However, it would be desirable to have a corrosion inhibitor which is useful in a broader number of situations. For example, highly concentrated hydrochloric acid is often employed in oil well stimulation treatment, but its use can lead to severe corrosion problems. Thus it would be desirable to have a corrosion inhibitor composition which could inhibit the acid corrosion of ferrous metals even in the presence of concentrated hydrochloric acid, and which is compatible with a variety of additives, for example, surfactants.